Magento 2 – How to Install and Configure Varnish

The answer I found is, Yes, a Varnish HIT should be recorded for cached pages in Magento 2 when Varnish is properly enabled. By properly, I mean:

• Varnish installed and running
• Magento 2 configured to use Varnish as FPC (Stores -> Configuration -> System -> "Full Page Cache"
• Download the vcl Magento gives you in the above admin area and load it into Varnish.
• Make sure that the "Page Cache" under System -> Cache Management is also enabled and refreshed.

To see the HIT in the HTTP response headers, you need to edit the vcl file and comment out the line:

unset resp.http.X-Varnish;

For Debug lines in the header response, put Magento into Developer mode, and make sure the resp.http.X-Magento-Debug is set (or unset commented out).

As well as installing mod_pagespeed you need to set it up correctly:

https://developers.google.com/speed/pagespeed/module/downstream-caching

You will also have to make sure your version of mod_pagespeed supports 'Varnish' as this is currently an 'experimental feature'.